Solid-state imaging device and driving method thereof, and electronic apparatus

ABSTRACT

A solid-state imaging device includes a photoelectric conversion unit, a light shielding unit and a transfer transistor. The photoelectric conversion unit generates charges by photoelectrically converting light. The light shielding unit is formed by engraving a semiconductor substrate on which the photoelectric conversion unit is formed, so as to surround an outer periphery of the photoelectric conversion unit. The transfer transistor transfers charges generated in the photoelectric conversion unit. During a charge accumulation period in which charges are accumulated in the photoelectric conversion unit, a potential that repels the charges is supplied to the light shielding unit and a gate electrode of the transfer transistor. During a charge transfer period in which charges are transferred from the photoelectric conversion unit, a potential that repels the charges is supplied to the light shielding unit and a potential that attracts the charges is supplied to the gate electrode of the transfer transistor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/265,346, filed Feb. 1, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/630,735, filed Jun. 22, 2017, now U.S. Pat. No.10,237,503, which is a continuation of U.S. patent application Ser. No.14/311,985, filed Jun. 23, 2014, now U.S. Pat. No. 9,723,235, whichclaims the benefit of Japanese Priority Patent Application JP2013-136216 filed Jun. 28, 2013, the entire disclosures of which areincorporated herein by reference.

BACKGROUND

The present disclosure relates to a solid-state imaging device and adriving method thereof, and an electronic apparatus, and in particular,to a solid-state imaging device and a driving method thereof, and anelectronic apparatus, capable of improving characteristics of pixels.

In the related art, in electronic apparatuses with imaging functions,such as digital still cameras and digital video cameras, solid-stateimaging devices such as, a Charge Coupled Device (CCD) and aComplementary Metal Oxide Semiconductor (CMOS) image sensor are used.The solid-state imaging devices include a pixel in which a photodiode(PD) performing photoelectric conversion and a plurality of transistorsare combined and an image is formed based on pixel signals which areoutput from a plurality of the pixels which are arranged in a planemanner.

For example, in the solid-state imaging device, charges accumulated inthe PD are transferred to a Floating Diffusion (FD) unit having apredetermined capacity which is provided in a connection portion betweenthe PD and a gate electrode of an amplifying transistor. Then, signalscorresponding to a level of the charges stored in the FD unit are readfrom the pixel and AD-converted by an Analog Digital (AD) conversioncircuit having a comparator so as to output the AD-converted signals.

In recent years, the solid-state imaging devices tend to have manypixels. Thus, when a pixel miniaturization is intended without changingthe chip size, there is a problem that the light incidentcharacteristics deteriorate and color mixing occurs between pixels.

For example, Japanese Unexamined Patent Application Publication No.2010-169911 discloses a solid-state imaging device which performs anelement separation optically and electrically by embedding aninter-pixel element separation film and a pixel light shielding film ona side on which light of a PD is incident, in order to reduce the colormixing between pixels. Further, Japanese Unexamined Patent ApplicationPublication No. 2011-40531 discloses a solid-state imaging device thatsuppresses generation of a dark current by employing a fixed chargefilm.

Further, it has been known that the color mixing between pixels can besignificantly reduced by employing an embedding technology in thesolid-state imaging device.

Furthermore, Japanese Unexamined Patent Application Publication No.2004-306144 discloses a solid-state imaging device that assists a chargetransfer, for example, by applying a voltage to a poly-silicon embeddedin a trench portion other than a drive signal of a normal pixel.

Further, it is possible to intend to suppress the dark current, toimprove a saturation charge amount, and to realize a low voltage drive,by applying a voltage to the trench portion.

In addition, Japanese Unexamined Patent Application Publication No.2007-25807 discloses a solid-state imaging device capable of intendingto suppress the dark current and of improving the saturation chargeamount, by providing electrodes in an upper part and a lower part of thePD so as to apply a suitable voltage.

SUMMARY

However, in the solid-state imaging devices described above, it is notassumed that a potential is applied to a light shielding film and thereis a problem that optical color mixing between pixels deteriorates whena pixel miniaturization is processed. Thus, the characteristics of thepixels deteriorate.

The present disclosure is made in view of such circumstances andintended to improve the characteristics of pixels.

According to an embodiment of the present disclosure, there is provideda solid-state imaging device including: a photoelectric conversion unitthat generates charges by photoelectrically converting light; a lightshielding unit that is formed by engraving a semiconductor substrate onwhich the photoelectric conversion unit is formed, so as to surround anouter periphery of the photoelectric conversion unit; and a transfertransistor that transfers charges generated in the photoelectricconversion unit, wherein during a charge accumulation period in whichcharges are accumulated in the photoelectric conversion unit, apotential that repels the charges is supplied to the light shieldingunit and a gate electrode of the transfer transistor, and wherein duringa charge transfer period in which charges are transferred from thephotoelectric conversion unit, a potential that repels the charges issupplied to the light shielding unit and a potential that attracts thecharges is supplied to the gate electrode of the transfer transistor.

According to another embodiment of the present disclosure, there isprovided a driving method of a solid-state imaging device including aphotoelectric conversion unit that generates charges byphotoelectrically converting light, a light shielding unit that isformed by engraving a semiconductor substrate on which the photoelectricconversion unit is formed, so as to surround an outer periphery of thephotoelectric conversion unit, and a transfer transistor that transferscharges generated in the photoelectric conversion unit, including:supplying a potential that repels the charges to the light shieldingunit and a gate electrode of the transfer transistor, during a chargeaccumulation period in which charges are accumulated in thephotoelectric conversion unit; and supplying a potential that repels thecharges to the light shielding unit and supplying a potential thatattracts the charges to the gate electrode of the transfer transistor,during a charge transfer period in which charges are transferred fromthe photoelectric conversion unit.

According to still another embodiment of the present disclosure, thereis provided an electronic apparatus including: a solid-state imagingdevice including a photoelectric conversion unit that generates chargesby photoelectrically converting light; a light shielding unit that isformed by engraving a semiconductor substrate on which the photoelectricconversion unit is formed, so as to surround an outer periphery of thephotoelectric conversion unit; and a transfer transistor that transferscharges generated in the photoelectric conversion unit, wherein during acharge accumulation period in which charges are accumulated in thephotoelectric conversion unit, a potential that repels the charges issupplied to the light shielding unit and a gate electrode of thetransfer transistor, and wherein during a charge transfer period inwhich charges are transferred from the photoelectric conversion unit, apotential that repels the charges is supplied to the light shieldingunit and a potential that attracts the charges is supplied to the gateelectrode of the transfer transistor.

In the embodiments, during a charge accumulation period in which chargesare accumulated in the photoelectric conversion unit, a potential thatrepels the charges is supplied to the light shielding unit and a gateelectrode of the transfer transistor, and during a charge transferperiod in which charges are transferred from the photoelectricconversion unit, a potential that repels the charges is supplied to thelight shielding unit and a potential that attracts the charges issupplied to the gate electrode of the transfer transistor.

According to the embodiments of the present disclosure, it is possibleto improve characteristics of pixels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration example of asolid-state imaging device according to an embodiment of the presenttechnology;

FIGS. 2A to 2C are diagrams illustrating a first configuration exampleof a pixel;

FIGS. 3A and 3B are diagrams illustrating an operation of a potentialapplied during a charge accumulation period and during a charge transferperiod;

FIG. 4 is a diagram illustrating a circuit configuration of a pixel;

FIG. 5 is a diagram illustrating a drive signal supplied to a pixel andpotentials of respective units in the pixel;

FIGS. 6A to 6C are diagrams illustrating a second configuration exampleof a pixel;

FIGS. 7A and 7B are diagrams illustrating an operation of a potentialapplied during a charge accumulation period and during a charge transferperiod;

FIG. 8 is a diagram illustrating a circuit configuration of a pixel;

FIG. 9 is a diagram illustrating a drive signal supplied to a pixel andpotentials of respective units in the pixel;

FIGS. 10A to 10C are diagrams illustrating a third configuration exampleof a pixel;

FIGS. 11A and 11B are diagrams illustrating an operation of a potentialapplied during a charge accumulation period and during a charge transferperiod;

FIG. 12 is a diagram illustrating a circuit configuration of a pixel;

FIG. 13 is a diagram illustrating a drive signal supplied to a pixel andpotentials of respective units in the pixel;

FIGS. 14A to 14C are diagrams illustrating a fourth configurationexample of a pixel;

FIGS. 15A and 15B are diagrams illustrating an operation of a potentialapplied during a charge accumulation period and during a charge transferperiod;

FIG. 16 is a diagram illustrating a circuit configuration of a pixel;

FIG. 17 is a diagram illustrating a drive signal supplied to a pixel andpotentials of respective units in the pixel;

FIGS. 18A to 18C are diagrams illustrating a fifth configuration exampleof a pixel;

FIGS. 19A and 19B are diagrams illustrating an operation of a potentialapplied during a charge accumulation period and during a charge transferperiod;

FIG. 20 is a diagram illustrating a circuit configuration of a pixel;

FIG. 21 is a diagram illustrating a drive signal supplied to a pixel andpotentials of respective units in the pixel; and

FIG. 22 is a block diagram illustrating a configuration example of animaging apparatus mounted on an electronic apparatus.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, specific embodiments to which the present technology isapplied will be described in detail with reference to drawings.

FIG. 1 is a block diagram illustrating a configuration example of anembodiment of a solid-state imaging device according to an embodiment ofthe present technology.

As illustrated in FIG. 1, a solid-state imaging device 11 is a CMOS-typesolid-state imaging device, and is configured to include a pixel arrayunit 12, a vertical driving unit 13, a column processing unit 14, ahorizontal driving unit 15, an output unit 16, and a driving controlunit 17.

The pixel array unit 12 includes a plurality of pixels 21 which arearranged in an array shape, is connected to the vertical driving unit 13through a plurality of horizontal signal lines 22 corresponding to thenumber of rows of the pixel 21, and is connected to the columnprocessing unit 14 through a plurality of vertical signal lines 23corresponding to the number of columns of the pixel 21. In other words,the plurality of pixels 21 included in the pixel array unit 12 arerespectively disposed at points in which the horizontal signal lines 22and the vertical signal lines 23 intersect.

The vertical driving unit 13 sequentially supplies drive signals fordriving (transferring, selecting, resetting, or the like) the respectivepixels 21 to respective rows of the plurality of pixels 21 included inthe pixel array unit 12 through the horizontal signal line 22.

The column processing unit 14 extracts the signal levels of pixelsignals by performing a Correlated Double Sampling (CDS) process on thepixel signals which are output from the respective pixels 21 andacquires pixel data corresponding to the amount of received light of thepixels 21, through the vertical signal line 23.

The horizontal driving unit 15 sequentially supplies the columnprocessing unit 14 with drive signals for outputting the pixel datawhich is acquired from the respective pixels 21 from the columnprocessing unit 14, for each column of the plurality of pixels 21included in the pixel array unit 12.

The pixel data is supplied from the column processing unit 14 to theoutput unit 16 at a timing corresponding to the drive signal of thehorizontal driving unit 15, and the output unit 16 amplifies, forexample, the pixel data and outputs the amplified pixel data to an imageprocessing circuit in the subsequent stage.

The driving control unit 17 controls the driving of each block in thesolid-state imaging device 11. For example, the driving control unit 17generates a block signal according to the driving period of each blockand supplies the block signal to each block.

FIGS. 2A to 2C are diagrams illustrating a first configuration exampleof a pixel 21 included in a solid-state imaging device 11.

FIG. 2A illustrates a cross-sectional configuration example of the pixel21 which is the first configuration example. In addition, light isincident on the pixel 21 from the top in FIG. 2A, and hereinafter,appropriately, a surface on a side on which light is incident isreferred to as a light incident surface, and a surface facing the sideopposite to the light incident surface is referred to as an oppositesurface. Further, FIG. 2B illustrates a planar configuration example ofthe solid-state imaging device 11 as viewed from the opposite surfaceside, and FIG. 2C illustrates a planar configuration example of thesolid-state imaging device 11 as viewed from the light incident surfaceside.

As illustrated in FIGS. 2A to 2C, the pixel 21 is configured with awiring layer 31 and a sensor layer 32 which are laminated, and a colorfilter layer and an on-chip lens layer, which are not shown, arelaminated on the light incident surface side of the sensor layer 32.

The wiring layer 31 includes a plurality of layers of wirings 41 formedbetween interlayer insulating films 42, and three layers of wirings 41-1to 41-3 are formed in a configuration example of FIGS. 2A to 2C.

In the sensor layer 32, a PD 52 and an FD unit 53 are formed on asemiconductor substrate 51, a gate electrode 54 is laminated on theopposite surface side of the semiconductor substrate 51, a fixed chargefilm 55 is laminated on the light incident surface side of thesemiconductor substrate 51, and an engraved light shielding electrode 57is formed in a trench formed on the light incident surface of thesemiconductor substrate 51, through the fixed charge film 55 and abarrier metal 56.

The semiconductor substrate 51 is a silicon substrate (P well) to whichP-type impurities are injected. The PD 52 is formed by a PN junctionformed by N-type impurities being injected to the semiconductorsubstrate 51, and generates charges by photoelectrically converting thereceived light to accumulate the generated charges.

The FD unit 53 is a dense N-type region (floating diffusion region)formed by injecting N-type impurities in the vicinity of the oppositesurface of the semiconductor substrate 51, and temporarily stores thecharges transferred from the PD 52. Further, the FD unit 53 is a chargedetection unit that converts the charges into a voltage, and the chargesstored in the FD unit 53 are converted into a voltage in an amplifyingtransistor (an amplifying transistor 62 in FIG. 4 which will bedescribed later). The gate electrode 54 is an electrode constituting agate of a transfer transistor (a transfer transistor 61 in FIG. 4 whichwill be described later) which transfers charges accumulated in the PD52 to the FD unit 53.

The fixed charge film 55 is a film that holds, for example, negativefixed charges, and suppresses the generation of a dark current at aboundary surface of the semiconductor substrate 51. In addition, aninsulating film may be used instead of the fixed charge film 55. Thebarrier metal 56 is a metal film which is formed for diffusionpreventing or interaction preventing of a metal material forming theengraved light shielding electrode 57.

For example, as illustrated in FIG. 2C, the engraved light shieldingelectrode 57 is formed so as to surround the outer periphery of the PD52. For example, an engraved light shielding film 55 is formed in such amanner that a trench is formed so as to surround the PD 52 on the lightincident surface of the semiconductor substrate 51, the fixed chargefilm 55 and the barrier metal 56 are formed on the inside of the trench,and then a metal having a light shielding property is embedded in thetrench.

Accordingly, the engraved light shielding electrode 57 can prevent theoccurrence of an optical crosstalk and an electric crosstalk with otheradjacent pixels 21. In other words, the engraved light shieldingelectrode 57 can prevent the light incident on the pixel 21 from leakingto other pixels 21, and prevent charges generated by photoelectricconversion in the pixel 21 from leaking to other pixels 21.

Further, the vertical driving unit 13 is connected to the engraved lightshielding electrode 57 through the horizontal signal line 22 of FIG. 1,and a potential of a level corresponding to the signal supplied from thevertical driving unit 13 is applied to the engraved light shieldingelectrode 57. For example, a negative potential is applied to theengraved light shielding electrode 57, during a charge accumulationperiod in which charges are accumulated in the PD 52, and during acharge transfer period in which charges are transferred from the PD 52to the FD unit 53. Further, a negative potential is applied to the gateelectrode 54 during the charge accumulation period, and a positivepotential is applied to the gate electrode 54 during the charge transferperiod.

An operation of a potential applied during the charge accumulationperiod and during the charge transfer period will be described withreference to FIGS. 3A and 3B.

FIG. 3A illustrates the pixel 21 during the charge accumulation period,and FIG. 3B illustrates the pixel 21 during the charge transfer period.In addition, the light incident on the pixel 21 is converted intoelectrons e in the PD 52. Further, as illustrated in FIGS. 3A and 3B,the light incident on the pixel 21 in an oblique direction is preventedfrom leaking to other adjacent pixels 21 by being reflected on theengraved light shielding electrode 57.

As illustrated in FIG. 3A, in the pixel 21, a force pushing electrons eto the center of the PD 52 is generated as indicated by the hollowarrows by applying negative potentials (potentials that repel electronse) to the gate electrode 54 and the engraved light shielding electrode57 during the charge accumulation period. Accordingly, the pixel 21 candeepen the potential well of the PD 52 during the charge accumulationperiod and increase the saturation charge amount of the PD 52. Further,in the pixel 21, it is possible to suppress the generation of a darkcurrent by applying a negative potential.

Further, during the charge transfer period, in the pixel 21, a negativepotential is applied to the engraved light shielding electrode 57,whereas a positive potential (the potential of attracting electrons e)is applied to the gate electrode 54. Thus, as indicated by the hollowarrows in FIG. 3B, a force pushing electrons e to the center of the PD52 and the gate electrode 54 is generated. Accordingly, as indicated bythe hollow arrow illustrated in dashed lines in FIG. 3B, in the pixel21, it is possible to assist the flow of the electrons e to the gateelectrode 54, and to improve the transfer performance of charges fromthe PD 52 to the FD unit 53.

In this manner, it is possible to increase the saturation charge amountof the PD 52 and to suppress the generation of a dark current during thecharge accumulation period, whereas it is possible to improve thetransfer performance of charges during the charge transfer period,thereby improving the characteristics of the pixel 21. Thus, forexample, it is possible to improve an S/N ratio and to reduce noise atlow light conditions in the pixel 21.

Further, in the solid-state imaging device 11, the materials used in theengraved light shielding electrode 57 on the light incident surface sidecan be used, for example, for light shielding in an optical blackregion. Thus, it is possible to reduce the number of steps in theproduction of the solid-state imaging device 11. Further, it is possibleto control the overflows of charges to other adjacent pixels 21 in thesolid-state imaging device 11.

Next, a driving method of the pixel 21 will be described with referenceto FIGS. 4 and 5.

FIG. 4 illustrates a circuit configuration of the pixel 21. FIG. 5illustrates a drive signal supplied to the pixel 21 and potentials ofrespective units in the pixel 21.

As illustrated in FIG. 4, the pixel 21 is configured to include atransfer transistor 61, an amplifying transistor 62, a selectiontransistor 63, and a reset transistor 64 as well as the PD 52, the FDunit 53, the gate electrode 54, and the engraved light shieldingelectrode 57, which are described with reference to FIGS. 2A to 2C, andis connected to the vertical signal line 23.

The transfer transistor 61 is driven according to a transfer signal TGsupplied from the vertical driving unit 13 of FIG. 1, and if thetransfer signal TG supplied to the gate electrode 54 of the transfertransistor 61 is at a high level, the transfer transistor 61 is turnedON. Thus, the charges accumulated in the PD 52 are transferred to the FDunit 53 through the transfer transistor 61.

The amplifying transistor 62 is an input portion of a source followerwhich is a reading circuit that reads signals obtained by thephotoelectric conversion in the PD 52, and outputs pixel signals of alevel corresponding to the charges accumulated in the FD unit 53 to thevertical signal line 23. In other words, the amplifying transistor 62constitutes the source follower with a current source (not shown)connected to one end of the vertical signal line 23 by the drainelectrode of the amplifying transistor 62 being connected to the powersupply voltage through the selection transistor 63 and the sourceelectrode thereof being connected to the vertical signal line 23.

The selection transistor 63 is driven according to a selection signalSEL supplied from the vertical driving unit 13 of FIG. 1, and if theselection signal SEL supplied to the gate electrode is at a high level,the selection transistor 63 is turned ON and the power supply voltage isconnected to the amplifying transistor 62.

The reset transistor 64 is driven according to a reset signal RESsupplied from the vertical driving unit 13 of FIG. 1. For example, ifthe reset signal RES supplied to the gate electrode is at a high level,the reset transistor 64 is turned ON, and resets the FD unit 53 bydischarging the charges accumulated in the FD unit 53 to the powersupply voltage.

Further, in the pixel 21, as described above with reference to FIGS. 3Aand 3B, a light shielding electrode applying voltage V_(RD) is suppliedfrom the vertical driving unit 13 to the engraved light shieldingelectrode 57 in order to apply the potential to the engraved lightshielding electrode 57.

FIG. 5 illustrates, in order from the top, the selection signal SEL, thereset signal RES, the transfer signal TG, the light shielding electrodeapplying voltages V_(RD)(1) and V_(RD)(2), the potential level V_(FD) ofthe FD unit 53, and the potential level V_(SIG) of the vertical signalline 23. In addition, in FIG. 5, inverted signals (that is, −V_(RD)(1)and −V_(RD)(2)) are illustrated as the light shielding electrodeapplying voltages V_(RD)(1) and V_(RD)(2), and when the applying voltageis at a high level, a negative potential is applied to the engravedlight shielding electrode 57.

Here, it is possible to select either the light shielding electrodeapplying voltage V_(RD)(1) or the light shielding electrode applyingvoltage V_(RD)(2) for use in response to the operation of the pixel 21.For example, the light shielding electrode applying voltage V_(RD)(1) isselected for use in a case of performing a normal expected operation,and the light shielding electrode applying voltage V_(RD)(2) is selectedfor use in a case of performing a pinning enhancement operation and atransfer assist enhancement operation.

Further, in FIG. 5, a timing t1 is a timing at which selecting the pixel21 as a pixel which outputs a pixel signal is started, and a timing t2is a timing at which charge transfer from the PD 52 to the FD unit 53 isstarted. Further, a timing t3 is a timing at which selecting the pixel21 as a pixel which outputs a pixel signal is terminated.

First, if the accumulation of charges of the PD 52 is started before thetiming t1 at which selecting the pixel 21 is started, the lightshielding electrode applying voltage V_(RD)(1) is switched from the lowlevel to the high level. Similarly, the light shielding electrodeapplying voltage V_(RD)(2) is switched from a low level to a first highlevel. Thus, a negative potential is applied to the engraved lightshielding electrode 57. In addition, the low level of the transfersignal TG is set to a negative potential and during a period other thanthe charge transfer period, a negative potential is applied to the gateelectrode 54 of the transfer transistor 61 according to the transfersignal TG.

Accordingly, during a period of accumulation of charges in the PD 52, anegative potential is applied to the gate electrode 54 and the engravedlight shielding electrode 57, and as illustrated in FIG. 3A, a forcepushing electrons e to the center of the PD 52 is generated.

Then, at the timing t1, the selection signal SEL is at a high level suchthat the pixel 21 is selected; and the reset signal RES is at a highlevel such that the potential level V_(FD) of the FD unit 53 is reset.In other words, the FD unit 53 is in a state in which chargestransferred to the FD unit 53 prior to the present process are left, andthe charges are discharged to the power supply voltage. As a consequenceof this, the potential level V_(SIG) of the vertical signal line 23varies depending on the potential level V_(FD) (that is, a reset level)of the FD unit 53. Thereafter, the reset signal RES is at a low leveland the potential level V_(FD) of the FD unit 53 and the potential levelV_(SIG) of the vertical signal line 23 are stable, and then thepotential level V_(SIG) of the vertical signal line 23 is read as apotential of a reset level to the column processing unit 14 of FIG. 1.

Next, at the timing t2, the transfer signal TG is at a high level suchthat the charges accumulated in the PD 52 are transferred to the FD unit53. In other words, at this time, a positive potential is applied to thegate electrode 54 of the transfer transistor 61 according to thetransfer signal TG. Accordingly, when charges are transferred from thePD 52, a negative potential is applied to the engraved light shieldingelectrode 57, whereas a positive potential is applied to the gateelectrode 54, such that, as illustrated in FIG. 3B, the flow ofelectrons e to the gate electrode 54 is assisted.

Further, at the timing t2, the light shielding electrode applyingvoltage V_(RD)(2) is switched from the first high level to a second highlevel of a higher level. Accordingly, if the light shielding electrodeapplying voltage V_(RD)(2) is selected for use, when charges aretransferred from the PD 52, a negative potential corresponding to thesecond high level which is higher than the negative potentialcorresponding to the first high level is applied to the engraved lightshielding electrode 57.

Then, if charges are transferred from the PD 52 to the FD unit 53, thepotential level V_(FD) of the FD unit 53 and the potential level V_(SIG)of the vertical signal line 23 vary depending on the amount of chargestransferred to the FD unit 53. Thereafter, the transfer signal TG is ata low level and the transfer of charges is terminated and thus thepotential level V_(FD) of the FD unit 53 and the potential level V_(SIG)of the vertical signal line 23 are stable, and then the potential levelV_(SIG) of the vertical signal line 23 is read out to the columnprocessing unit 14 of FIG. 1 as a potential of the pixel signal level.

Thereafter, at the timing t3, the selection signal SEL is at a low leveland thus the selection of the pixel 21 is terminated. At this time, thelight shielding electrode applying voltage V_(RD)(1) is switched from ahigh level to a low level, and the light shielding electrode applyingvoltage V_(RD)(2) is switched from the second high level to the lowlevel.

Further, when the light shielding electrode applying voltage V_(RD)(2)is selected as a voltage to be applied to the engraved light shieldingelectrode 57, during the charge transfer period, a negative potential ofthe second high level which is at a higher level than the first highlevel during the charge accumulation period is applied to the engravedlight shielding electrode 57. Thus, the transfer assist of charge can befurther enhanced.

Next, FIGS. 6A to 6C are diagrams illustrating a second configurationexample of the pixel 21 included in the solid-state imaging device 11.

FIG. 6A illustrates a cross-sectional configuration example of the pixel21-1 which is the second configuration example, FIG. 6B illustrates aplanar configuration example of the pixel 21-1 as viewed from theopposite surface side, and FIG. 6C illustrates a planar configurationexample of the pixel 21-1 as viewed from the light incident surfaceside.

As illustrated in FIGS. 6A to 6C, the pixel 21-1 has a differentconfiguration from the pixel 21 of FIGS. 2A to 2C in that a planarelectrode 72 is laminated through an insulating film 71 on the oppositesurface side of the semiconductor substrate 51 and a transparentconductive film 74 is laminated through a barrier metal 73 on a lightincident surface side of the semiconductor substrate 51.

In addition, otherwise, the pixel 21-1 has common components with thepixel 21 of FIGS. 2A to 2C, the common components are denoted by thesame reference numerals and thus the detailed description thereof willbe omitted. In other words, the pixel 21-1 has a configuration common tothe pixel 21 of FIGS. 2A to 2C in that the PD 52 and the FD unit 53 areformed on the semiconductor substrate 51, the gate electrode 54 islaminated on the opposite surface side of the semiconductor substrate51, the fixed charge film 55 is laminated on the light incident surfaceside of the semiconductor substrate 51, and the engraved light shieldingelectrode 57 is formed in the trench which is formed on the lightincident surface of the semiconductor substrate 51, through the fixedcharge film 55 and the barrier metal 56.

The insulating film 71 is a film having an insulating property andinsulates a part between the semiconductor substrate 51 and the planarelectrode 72. The planar electrode 72 is an electrode disposed in aplane manner with respect to the opposite surface of the sensor layer32, and as illustrated in FIG. 6B, is configured so as to cover theentire surface of the pixel 21-1 other than a region in which the FDunit 53 and the gate electrode 54 are formed, on the opposite surface ofthe sensor layer 32.

The barrier metal 73 is a metal film which is formed for diffusionprevention or interaction prevention of a metal material forming thetransparent conductive film 74. The transparent conductive film 74 is afilm having optical transparency and electrical conductivity, and isformed so as to cover the entire surface of the pixel 21-1 in the lightincident surface of the sensor layer 32.

Then, in the pixel 21-1, the vertical driving unit 13 is respectivelyconnected to the planar electrode 72 and the transparent conductive film74 through a horizontal signal line 22 of FIG. 1, and a potential of alevel corresponding to signals supplied from the vertical driving unit13 is applied thereto. For example, a negative potential is applied tothe planar electrode 72 during the charge accumulation period, and apositive potential is applied thereto during the charge transfer period.Further, a negative potential is applied to the transparent conductivefilm 74, during the charge accumulation period and during the chargetransfer period.

An operation of a potential applied during the charge accumulationperiod and during the charge transfer period will be described withreference to FIGS. 7A and 7B.

FIG. 7A illustrates the pixel 21-1 during the charge accumulationperiod, and FIG. 7B illustrates the pixel 21-1 during the chargetransfer period. In addition, the light incident on the pixel 21-1 isconverted into electrons e in the PD 52. Further, as illustrated inFIGS. 7A and 7B, the light incident on the pixel 21-1 in an obliquedirection is prevented from leaking to other adjacent pixels 21 by beingreflected on the engraved light shielding electrode 57.

As illustrated in FIG. 7A, in the pixel 21-1, a negative potential isapplied to the gate electrode 54, the engraved light shielding electrode57, the planar electrode 72, and the transparent conductive film 74during the charge accumulation period. Thus, as indicated by the hollowarrows in FIG. 7A, a force pushing electrons e to the center of the PD52 is generated. Accordingly, the pixel 21-1 can deepen the potentialwell of the PD 52 during the charge accumulation period and increase thesaturation charge amount of the PD 52. Further, in the pixel 21-1, it ispossible to suppress the generation of a dark current by applying anegative potential.

Further, during the charge transfer period, in the pixel 21-1, anegative potential is applied to the engraved light shielding electrode57 and the transparent conductive film 74, whereas a positive potentialis applied to the gate electrode 54 and the planar electrode 72. Thus,as indicated by the hollow arrows in FIG. 7B, a force pushing electronse to the center of the PD 52 and to the opposite surface is generated.Accordingly, as indicated by the hollow arrows of a dashed line in FIG.7B, in the pixel 21-1, it is possible to assist the flow of theelectrons e to the gate electrode 54 which is located on the oppositesurface, and to improve the transfer performance of charges from the PD52 to the FD unit 53.

In this manner, it is possible to increase the saturation charge amountof the PD 52 and to suppress the generation of a dark current during thecharge accumulation period, whereas it is possible to improve thetransfer performance of charges during the charge transfer period,thereby improving the characteristics of the pixel 21-1.

Next, a driving method of the pixel 21-1 will be described withreference to FIGS. 8 and 9.

FIG. 8 illustrates a circuit configuration of the pixel 21-1. FIG. 9illustrates a drive signal supplied to the pixel 21-1 and potentials ofrespective units in the pixel 21-1.

As illustrated in FIG. 8, the pixel 21-1 has a different configurationfrom the pixel 21 of FIG. 4 in that a planar electrode 72 is disposed onthe opposite surface side of the sensor layer 32 and a transparentconductive film 74 is disposed on the light incident surface side of thesensor layer 32. In addition, the pixel 21-1 has common components withthe pixel 21 of FIG. 4 in other parts, the common components are denotedby the same reference numerals and thus the detailed description thereofwill be omitted. In other words, the pixel 21-1 is configured to includea transfer transistor 61, an amplifying transistor 62, a selectiontransistor 63, and a reset transistor 64, and is connected to a verticalsignal line 23.

Further, in the pixel 21-1, a planar electrode applying voltage V_(TSF)is supplied from the vertical driving unit 13 to the planar electrode 72in order to apply the potentials, described with reference to FIGS. 7Aand 7B, to the planar electrode 72. Similarly, in the pixel 21-1, atransparent conductive film applying voltage V_(TR) is supplied from thevertical driving unit 13 to the transparent conductive film 74 in orderto apply the potentials, described with reference to FIGS. 7A and 7B, tothe transparent conductive film 74.

FIG. 9 illustrates, in order from the top, the selection signal SEL, thereset signal RES, the transfer signal TG, the light shielding electrodeapplying voltages V_(RD)(1) and V_(RD)(2), the transparent conductivefilm applying voltages V_(TR)(1) and V_(TR)(2), the planar electrodeapplying voltages V_(TSF)(1) and V_(TSF)(2), the potential level V_(FD)of the FD unit 53, and the potential level V_(SIG) of the verticalsignal line 23.

Here, the light shielding electrode applying voltage V_(RD)(1) and thetransparent conductive film applying voltage V_(TR)(1) are common, andthe light shielding electrode applying voltage V_(RD)(2) and thetransparent conductive film applying voltage V_(TR)(2) are common.Further, the light shielding electrode applying voltages V_(RD)(1) andV_(RD)(2) and the transparent conductive film applying voltagesV_(TR)(1) and V_(RD)(2) are represented as inverted signals, and whenthe applying voltage is a high level, a negative potential is applied.In addition, the low level of the planar electrode applying voltagesV_(TSF)(1) and V_(TSF)(2) is a negative potential, and the high level ofthe planar electrode applying voltages V_(TSF)(1) and V_(TSF)(2) is apositive potential.

Further, it is possible to select either a pair of the light shieldingelectrode applying voltage V_(RD)(1) and transparent conductive filmapplying voltage V_(TR)(1) or a pair of the light shielding electrodeapplying voltage V_(RD)(2) and the transparent conductive film applyingvoltage V_(TR)(2) for use in response to the operation of the pixel21-1. For example, the light shielding electrode applying voltageV_(RD)(1) and the transparent conductive film applying voltage V_(TR)(1)are selected for use in a case of performing a normal expectedoperation. In contrast, the light shielding electrode applying voltageV_(RD)(2) and the transparent conductive film applying voltage V_(TR)(2)are selected for use in a case of performing a pinning enhancementoperation and a transfer assist enhancement operation.

In the same manner, it is possible to select either the planar electrodeapplying voltage V_(TSF)(1) or the planar electrode applying voltageV_(TSF)(2) for use in response to the operation of the pixel 21-1. Forexample, the planar electrode applying voltage V_(TSF)(1) is selectedfor use in a case of performing a normal expected operation, and theplanar electrode applying voltage V_(TSF)(2) is selected for use in acase of performing an operation of performing a transfer after causingcharges to approach the vicinity of the opposite surface.

Further, in FIG. 9, a timing t1 is a timing at which selecting the pixel21-1 as a pixel which outputs a pixel signal is started, and a timing t2is a timing at which charge transfer from the PD 52 to the FD unit 53 isstarted. Further, a timing t3 is a timing at which selecting the pixel21-1 as a pixel which outputs a pixel signal is terminated.

First, if the accumulation of charges of the PD 52 is started before thetiming t1 at which selecting the pixel 21-1 is started, the lightshielding electrode applying voltage V_(RD)(1) and the transparentconductive film applying voltage V_(TR)(1) are switched from the lowlevel to the high level. Similarly, the light shielding electrodeapplying voltage V_(RD)(2) and the transparent conductive film applyingvoltage V_(TR)(2) are switched from the low level to a first high level.Thus, a negative potential is applied to the engraved light shieldingelectrode 57 and the transparent conductive film 74. Further, at thistime, the planar electrode applying voltages V_(TSF)(1) and V_(TSF)(2)are at a low level, a negative potential is applied to the planarelectrode 72. In addition, the low level of the transfer signal TG isset to a negative potential and during a period other than the chargetransfer period, a negative potential is applied to the gate electrode54 of the transfer transistor 61 according to the transfer signal TG.

Accordingly, during a period of accumulation of charges in the PD 52, anegative potential is applied to the gate electrode 54, the engravedlight shielding electrode 57, the transparent conductive film 74, andthe planar electrode 72, and as illustrated in FIG. 7A, a force pushingelectrons e to the center of the PD 52 is generated.

Then, at the timing t1, the selection signal SEL is at a high level suchthat the pixel 21-1 is selected; and the reset signal RES is at a highlevel such that the potential level V_(FD) of the FD unit 53 is reset.In other words, the FD unit 53 is in a state in which chargestransferred to the FD unit 53 prior to the present process are left, andthe charges are discharged to the power supply voltage. As a consequenceof this, the potential level V_(SIG) of the vertical signal line 23varies depending on the potential level V_(FD)(that is, a reset level)of the FD unit 53. Thereafter, the reset signal RES is at a low leveland the potential level V_(FD) of the FD unit 53 and the potential levelV_(SIG) of the vertical signal line 23 are stable, and then thepotential level V_(SIG) of the vertical signal line 23 is read as apotential of a reset level to the column processing unit 14 of FIG. 1.

Next, at the timing t2, the transfer signal TG is at a high level suchthat the charges accumulated in the PD 52 are transferred to the FD unit53. In other words, at this time, a positive potential is applied to thegate electrode 54 of the transfer transistor 61 according to thetransfer signal TG. Further, simultaneously with the transfer signal TG,the planar electrode applying voltage V_(TSF)(1) is at a high level suchthat a positive potential is applied to the planar electrode 72according to the planar electrode applying voltage V_(TSF)(1).

Accordingly, when charges are transferred from the PD 52, a negativepotential is applied to the engraved light shielding electrode 57 andthe transparent conductive film 74, whereas a positive potential isapplied to the gate electrode 54 and the planar electrode 72, such thatas illustrated in FIG. 7B, the flow of electrons e to the gate electrode54 is assisted.

Further, at the timing t2, the light shielding electrode applyingvoltage V_(RD)(2) and the transparent conductive film applying voltageV_(TR)(2) are switched from the first high level to a second high levelof a higher level. Accordingly, if the light shielding electrodeapplying voltage V_(RD)(2) and the transparent conductive film applyingvoltage V_(RD)(2) are selected for use, when charges are transferredfrom the PD 52, a negative potential corresponding to the second highlevel which is higher than the negative potential corresponding to thefirst high level is applied to the engraved light shielding electrode 57and the transparent conductive film 74.

Then, if charges are transferred from the PD 52 to the FD unit 53, thepotential level V_(FD) of the FD unit 53 and the potential level V_(SIG)of the vertical signal line 23 vary depending on the amount of chargestransferred to the FD unit 53. Thereafter, the transfer signal TG andthe planar electrode applying voltage V_(TSF)(1) are at a low level suchthat the transfer of charges is terminated and thus the potential levelV_(FD) of the FD unit 53 and the potential level V_(SIG) of the verticalsignal line 23 are stable, and then the potential level V_(SIG) of thevertical signal line 23 is read out to the column processing unit 14 ofFIG. 1 as a potential of the pixel signal level.

Here, the planar electrode applying voltage V_(TSF)(2) is at a highlevel at a predetermined timing later than the planar electrode applyingvoltage V_(TSF)(1). In other words, when the planar electrode applyingvoltage V_(TSF)(2) is selected for use, a positive potential is appliedto the planar electrode 72 at a timing later than a timing at which apositive potential is applied to the gate electrode 54. Thus, forexample, when charges are transferred from the PD 52 to the FD unit 53,electrons e are drawn to the opposite surface side of the semiconductorsubstrate 51 after the flow of electrons e to the gate electrode 54 isformed, such that the leakage of electrons e along the opposite surfaceof the semiconductor substrate 51 is prevented.

Thereafter, at the timing t3, the selection signal SEL is at a low leveland thus the selection of the pixel 21-1 is terminated. At this time,the light shielding electrode applying voltage V_(RD)(1) and thetransparent conductive film applying voltage V_(TR)(1) are switched froma high level to a low level. In the same manner, the light shieldingelectrode applying voltage V_(RD)(2) and the transparent conductive filmapplying voltage V_(TR)(2) are switched from the second high level tothe low level.

Next, FIGS. 10A to 10C are diagrams illustrating a third configurationexample of the pixel 21 included in the solid-state imaging device 11.

FIG. 10A illustrates a cross-sectional configuration example of thepixel 21-2 which is the third configuration example, FIG. 10Billustrates a planar configuration example of the pixel 21-2 as viewedfrom the opposite surface side, and FIG. 10C illustrates a planarconfiguration example of the pixel 21-2 as viewed from the lightincident surface side.

As illustrated in FIGS. 10A to 10C, the pixel 21-2 has a differentconfiguration from the pixel 21 of FIGS. 2A to 2C in that the engravedlight shielding electrode 57 is divided into the engraved lightshielding electrodes 57 a-1 and 57 a-2. In addition, otherwise, thepixel 21-2 has common components with the pixel 21 of FIGS. 2A to 2C,the common components are denoted by the same reference numerals andthus the detailed description thereof will be omitted. In other words,the pixel 21-2 has a configuration common to the pixel 21 of FIGS. 2A to2C in that the PD 52 and the FD unit 53 are formed on the semiconductorsubstrate 51 and the gate electrode 54 is laminated on the oppositesurface side of the semiconductor substrate 51.

As illustrated in FIG. 10C, the engraved light shielding electrode 57a-1 is formed to surround the three side surfaces of the PD 52, that is,to surround the side surfaces of the PD 52 other than the side surfaceon the side on which the FD unit 53 and the gate electrode 54 areformed. Further, the engraved light shielding electrode 57 a-2 is formedalong the side surface of the PD 52 on the side in which the FD unit 53and the gate electrode 54 are formed.

In other words, in the pixel 21-2, a first trench is formed along threeside surfaces other than the side surface of the PD 52 on the side inwhich the FD unit 53 and the gate electrode 54 are formed, from thelight incident surface of the semiconductor substrate 51, and a secondtrench is formed along the side surface of the PD 52 on the side inwhich the FD unit 53 and the gate electrode 54 are formed. Then, theengraved light shielding electrode 57 a-1 is formed in the first trenchthrough the fixed charge film 55 a and the barrier metal 56 a-1, and theengraved light shielding electrode 57 a-2 is formed in the second trenchthrough the fixed charge film 55 a and the barrier metal 56 a-2.

Then, in the pixel 21-2, the vertical driving unit 13 is connected tothe engraved light shielding electrodes 57 a-1 and 57 a-2 through thehorizontal signal line 22 of FIG. 1, and a potential of a levelcorresponding to signals supplied from the vertical driving unit 13 isapplied thereto. For example, a negative potential is applied to theengraved light shielding electrode 57 a-1 during the charge accumulationperiod and during the charge transfer period. Further, a negativepotential is applied to the engraved light shielding electrode 57 a-2during the charge accumulation period, and a positive potential isapplied to the engraved light shielding electrode 57 a-2 during thecharge transfer period.

An operation of a potential applied during the charge accumulationperiod and during the charge transfer period will be described withreference to FIGS. 11A and 11B.

FIG. 11A illustrates the pixel 21-2 during the charge accumulationperiod, and FIG. 11B illustrates the pixel 21-2 during the chargetransfer period. In addition, the light incident on the pixel 21-2 isconverted into electrons e in the PD 52. Further, as illustrated inFIGS. 11A and 11B, the light incident on the pixel 21-2 in an obliquedirection is prevented from leaking to other adjacent pixels 21 by beingreflected on the engraved light shielding electrode 57.

As illustrated in FIG. 11A, in the pixel 21-2, a negative potential isapplied to the gate electrode 54, the engraved light shielding electrode57 a-1, and the engraved light shielding electrode 57 a-2 during thecharge accumulation period. Thus, as indicated by the hollow arrows inFIG. 11A, a force pushing electrons e to the center of the PD 52 isgenerated. Accordingly, the pixel 21-2 can deepen the potential well ofthe PD 52 during the charge accumulation period and increase thesaturation charge amount of the PD 52. Further, in the pixel 21-2, it ispossible to suppress the generation of a dark current by applying anegative potential.

Further, during the charge transfer period, in the pixel 21-2, anegative potential is applied to the engraved light shielding electrode57 a-1, whereas a positive potential is applied to the gate electrode 54and the engraved light shielding electrode 57 a-2. Thus, as indicated bythe hollow arrows in FIG. 11B, a force pushing electrons e to a sidesurface on the engraved light shielding electrode 57 a-2 side and thegate electrode 54 is generated. Accordingly, as indicated by the hollowarrows of a dashed line in FIG. 11B, in the pixel 21-2, it is possibleto assist the flow of the electrons e to the gate electrode 54 which islocated on the engraved light shielding electrode 57 a-2 side, and toimprove the transfer performance of charges from the PD 52 to the FDunit 53.

In addition, during the charge transfer period, 0 V may be applied tothe engraved light shielding electrode 57 a-2. Even in this case, theflow of electrons e to the engraved light shielding electrode 57 a-2side is assisted by the negative potential applied to the engraved lightshielding electrode 57 a-1.

In this manner, it is possible to increase the saturation charge amountof the PD 52 and to suppress the generation of a dark current during thecharge accumulation period, whereas it is possible to improve thetransfer performance of charges during the charge transfer period,thereby improving the characteristics of the pixel 21-2.

Next, a driving method of the pixel 21-2 will be described withreference to FIGS. 12 and 13.

FIG. 12 illustrates a circuit configuration of the pixel 21-2. FIG. 13illustrates a drive signal supplied to the pixel 21-2 and potentials ofrespective units in the pixel 21-2.

As illustrated in FIG. 12, the pixel 21-2 has a different configurationfrom the pixel 21 of FIG. 4 in that an engraved light shieldingelectrode 57 a-2 is disposed on the FD unit 53 side of the PD 52, and anengraved light shielding electrode 57 a-1 is disposed on the oppositeside thereto. In addition, the pixel 21-2 has common components with thepixel 21 of FIG. 4 in other parts, the common components are denoted bythe same reference numerals and thus the detailed description thereofwill be omitted. In other words, the pixel 21-2 is configured to includea transfer transistor 61, an amplifying transistor 62, a selectiontransistor 63, and a reset transistor 64, and is connected to a verticalsignal line 23.

Further, in the pixel 21-2, light shielding electrode applying voltagesV_(RD1) and V_(RD2) are respectively supplied from the vertical drivingunit 13 to the engraved light shielding electrodes 57 a-1 and 57 a-2 inorder to apply the potentials described above with reference to FIGS.11A and 11B to the engraved light shielding electrodes 57 a-1 and 57a-2.

FIG. 13 illustrates, in order from the top, the selection signal SEL,the reset signal RES, the transfer signal TG, the light shieldingelectrode applying voltages V_(RD1)(1) and V_(RD1)(2), the lightshielding electrode applying voltages V_(RD2)(1) and V_(RD2)(2), thepotential level V_(FD) of the FD unit 53, and the potential levelV_(SIG) of the vertical signal line 23.

Here, it is possible to select either the light shielding electrodeapplying voltage V_(RD1)(1) or the light shielding electrode applyingvoltage V_(RD1)(2) for use in response to the operation of the pixel21-2. For example, the light shielding electrode applying voltageV_(RD1)(1) is selected for use in a case of performing a normal expectedoperation. In contrast, the light shielding electrode applying voltageV_(RD1)(2) is selected for use in a case of performing a pinningenhancement operation and a transfer assist enhancement operation. Inthe same manner, it is possible to select either the light shieldingelectrode applying voltage V_(RD2)(1) or the light shielding electrodeapplying voltage V_(RD2)(2) for use in response to the operation of thepixel 21-2. For example, the light shielding electrode applying voltageV_(RD2)(1) is selected for use in a case of performing a normal expectedoperation. In contrast, the light shielding electrode applying voltageV_(RD2)(2) is selected for use in a case of performing a transfer assistoperation of approaching the vicinity of the FD unit 53 once.

Further, in FIG. 13, a timing t1 is a timing at which selecting thepixel 21-2 as a pixel which outputs a pixel signal is started, and atiming t2 is a timing at which charge transfer from the PD 52 to the FDunit 53 is started. Further, a timing t3 is a timing at which selectingthe pixel 21-2 as a pixel which outputs a pixel signal is terminated.

First, if the accumulation of charges of the PD 52 is started before thetiming t1 at which selecting the pixel 21-2 is started, the lightshielding electrode applying voltage V_(RD1)(1) is switched from the lowlevel to the high level, and the light shielding electrode applyingvoltage V_(RD1)(2) is switched from the low level to the first highlevel. Further, similarly, the light shielding electrode applyingvoltages V_(RD2)(1) and V_(RD2)(2) are switched from the low level tothe high level. Thus, a negative potential is applied to the engravedlight shielding electrodes 57 a-1 and 57 a-2. In addition, the low levelof the transfer signal TG is set to a negative potential and during aperiod other than the charge transfer period, a negative potential isapplied to the gate electrode 54 of the transfer transistor 61 accordingto the transfer signal TG.

Accordingly, during a period of accumulation of charges in the PD 52, anegative potential is applied to the gate electrode 54 and the engravedlight shielding electrodes 57 a-1 and 57 a-2, and as illustrated in FIG.11A, a force pushing electrons e to the center of the PD 52 isgenerated.

Then, at the timing t1, the selection signal SEL is at a high level suchthat the pixel 21-2 is selected; and the reset signal RES is at a highlevel such that the potential level V_(FD) of the FD unit 53 is reset.In other words, the FD unit 53 is in a state in which chargestransferred to the FD unit 53 prior to the present process are left, andthe charges are discharged to the power supply voltage. As a consequenceof this, the potential level V_(SIG) of the vertical signal line 23varies depending on the potential level V_(FD) (that is, a reset level)of the FD unit 53. Thereafter, the reset signal RES is at a low leveland the potential level V_(FD) of the FD unit 53 and the potential levelV_(SIG) of the vertical signal line 23 are stable, and then thepotential level V_(SIG) of the vertical signal line 23 is read as apotential of a reset level to the column processing unit 14 of FIG. 1.

Next, at the timing t2, the transfer signal TG is at a high level suchthat the charges accumulated in the PD 52 are transferred to the FD unit53. In other words, at this time, a positive potential is applied to thegate electrode 54 of the transfer transistor 61 according to thetransfer signal TG. Further, simultaneously with the transfer signal TG,the light shielding electrode applying voltage V_(RD2)(1) is at a lowlevel such that a positive potential is applied to the engraved lightshielding electrode 57 a-2 according to the light shielding electrodeapplying voltage V_(RD2)(1).

Accordingly, when charges are transferred from the PD 52, a negativepotential is applied to the engraved light shielding electrode 57 a-1,whereas a positive potential is applied to the gate electrode 54 and theengraved light shielding electrode 57 a-2, such that as illustrated inFIG. 11B, the flow of electrons e to the gate electrode 54 located onthe engraved light shielding electrode 57 a-2 side is assisted.

Further, at the timing t2, the light shielding electrode applyingvoltage V_(RD1)(2) is switched from the first high level to a secondhigh level of a higher level. Accordingly, if the light shieldingelectrode applying voltage V_(RD1)(2) is selected for use, when chargesare transferred from the PD 52, a negative potential corresponding tothe second high level which is higher than the negative potentialcorresponding to the first high level is applied to the engraved lightshielding electrode 57 a-1.

In addition, the light shielding electrode applying voltage V_(RD2)(2)is at a low level at a predetermined timing before the timing t2, and apositive potential is applied to the engraved light shielding electrode57 a-2. Thus, prior to the charge transfer, an assist of causingelectrons e to approach the vicinity of the FD unit 53 is performedfirst.

Then, if charges are transferred from the PD 52 to the FD unit 53, thepotential level V_(FD) of the FD unit 53 and the potential level V_(SIG)of the vertical signal line 23 vary depending on the amount of chargestransferred to the FD unit 53. Thereafter, the transfer signal TG is ata low level and the transfer of charges is terminated and the potentiallevel V_(FD) of the FD unit 53 and the potential level V_(SIG) of thevertical signal line 23 are stable, and then the potential level V_(SIG)of the vertical signal line 23 is read out to the column processing unit14 of FIG. 1 as a potential of the pixel signal level.

Thereafter, at the timing t3, the selection signal SEL is at a low leveland thus the selection of the pixel 21-2 is terminated. At this time,the light shielding electrode applying voltage V_(RD1)(1) is switchedfrom a high level to a low level, and the light shielding electrodeapplying voltage V_(RD1)(2) is switched from the second high level tothe low level.

Next, FIGS. 14A to 14C are diagrams illustrating a fourth configurationexample of the pixel 21 included in the solid-state imaging device 11.

FIG. 14A illustrates a cross-sectional configuration example of thepixel 21-3 which is the fourth configuration example, FIG. 14Billustrates a planar configuration example of the pixel 21-3 as viewedfrom the opposite surface side, and FIG. 14C illustrates a planarconfiguration example of the pixel 21-3 as viewed from the lightincident surface side.

As illustrated in FIGS. 14A to 14C, the pixel 21-3 has a differentconfiguration from the pixel 21 of FIGS. 2A to 2C in that the engravedlight shielding electrode 57 is divided into the engraved lightshielding electrodes 57 b-1 and 57 b-2. In addition, otherwise, thepixel 21-3 has common components with the pixel 21 of FIGS. 2A to 2C,the common components are denoted by the same reference numerals andthus the detailed description thereof will be omitted. In other words,the pixel 21-3 has a configuration common to the pixel 21 of FIGS. 2A to2C in that a PD 52 and an FD unit 53 are formed on the semiconductorsubstrate 51 and a gate electrode 54 is laminated on an opposite surfaceside of the semiconductor substrate 51.

As illustrated in FIG. 14A, in the pixel 21-3, the engraved lightshielding electrode 57 b-2 is formed in a trench formed on the lightincident surface side of the semiconductor substrate 51, whereas theengraved light shielding electrode 57 b-1 is formed in a trench formedon the opposite surface side of the semiconductor substrate 51. Then, asillustrated in FIG. 14B, the engraved light shielding electrode 57 b-1is formed to surround the three side surfaces of the PD 52, that is, tosurround the side surfaces of the PD 52 other than the side surface onthe side in which the FD unit 53 and the gate electrode 54 are formed.Further, the engraved light shielding electrode 57 b-2 is formed alongthe side surface of the PD 52 on the side in which the FD unit 53 andthe gate electrode 54 are formed, and as illustrated in FIG. 14C, isformed to surround the PD 52 while being laminated on the light incidentsurface of the semiconductor substrate 51.

In other words, in the pixel 21-3, a first trench is formed along threeside surfaces other than the side surface of the PD 52 on the side inwhich the FD unit 53 and the gate electrode 54 are formed, from theopposite surface of the semiconductor substrate 51. Then, the engravedlight shielding electrode 57 b-1 is formed in the first trench throughthe fixed charge film 55 b-1 and the barrier metal 56 b-1.

In other words, in the pixel 21-3, a second trench is formed along theside surface of the PD 52 on the side in which the FD unit 53 and thegate electrode 54 are formed, from the light incident surface of thesemiconductor substrate 51. Then, the engraved light shielding electrode57 b-2 is formed in the second trench through the fixed charge film 55b-2 and the barrier metal 56 b-2, and the engraved light shieldingelectrode 57 b-2 is formed to surround the PD 52 on the light incidentsurface of the semiconductor substrate 51 through the fixed charge film55 b-2.

Then, in the pixel 21-3, the vertical driving unit 13 is connected tothe engraved light shielding electrodes 57 b-1 and 57 b-2 through thehorizontal signal line 22 of FIG. 1, and a potential of a levelcorresponding to signals supplied from the vertical driving unit 13 isapplied thereto. For example, a negative potential is applied to theengraved light shielding electrode 57 b-1 during the charge accumulationperiod and during the charge transfer period. Further, a negativepotential is applied to the engraved light shielding electrode 57 a-2during the charge accumulation period, and 0 V is applied to theengraved light shielding electrode 57 a-2 during the charge transferperiod.

An operation of a potential applied during the charge accumulationperiod and during the charge transfer period will be described withreference to FIGS. 15A and 15B.

FIG. 15A illustrates the pixel 21-3 during the charge accumulationperiod, and FIG. 15B illustrates the pixel 21-3 during the chargetransfer period. In addition, the light incident on the pixel 21-3 isconverted into electrons e in the PD 52. Further, as illustrated inFIGS. 15A and 15B, the light incident on the pixel 21-3 in an obliquedirection is prevented from leaking to other adjacent pixels 21 by beingreflected on the engraved light shielding electrode 57.

As illustrated in FIG. 15A, in the pixel 21-3, a negative potential isapplied to the gate electrode 54, the engraved light shielding electrode57 b-1, and the engraved light shielding electrode 57 b-2 during thecharge accumulation period. Thus, as indicated by the hollow arrows inFIG. 15A, a force pushing electrons e to the center of the PD 52 isgenerated. Accordingly, the pixel 21-3 can deepen the potential well ofthe PD 52 during the charge accumulation period and increase thesaturation charge amount of the PD 52. Further, in the pixel 21-3, it ispossible to suppress the generation of a dark current by applying anegative potential.

Further, during the charge transfer period, in the pixel 21-3, anegative potential is applied to the engraved light shielding electrode57 b-1, whereas a positive potential is applied to the gate electrode54, and 0 V is applied to the engraved light shielding electrode 57 b-2.Thus, as indicated by the hollow arrows in FIG. 15B, a force pushingelectrons e from the engraved light shielding electrode 57 b-1 to theengraved light shielding electrode 57 b-2 and the gate electrode 54 isgenerated. Accordingly, as indicated by the hollow arrows of a dashedline in FIG. 15B, in the pixel 21-3, it is possible to assist the flowof the electrons e to the gate electrode 54 which is located on theengraved light shielding electrode 57 a-2 side, and to improve thetransfer performance of charges from the PD 52 to the FD unit 53.

In addition, a positive potential may be applied to the engraved lightshielding electrode 57 b-2 during the charge transfer period. Even inthis case, the flow of electrons e to the engraved light shieldingelectrode 57 a-2 side is assisted by the positive potential applied tothe engraved light shielding electrode 57 b-2. Further, when theengraved light shielding electrode 57 b-2 is located in the vicinity ofthe gate electrode 54, the flow of electrons e to the gate electrode 54is assisted by applying the negative potential to the engraved lightshielding electrode 57 b-2 during the charge transfer period.

In this manner, it is possible to increase the saturation charge amountof the PD 52 and to suppress the generation of a dark current during thecharge accumulation period, whereas it is possible to improve thetransfer performance of charges during the charge transfer period,thereby improving the characteristics of the pixel 21-3.

Next, a driving method of the pixel 21-3 will be described withreference to FIGS. 16 and 17.

FIG. 16 illustrates a circuit configuration of the pixel 21-3. FIG. 17illustrates a drive signal supplied to the pixel 21-3 and potentials ofrespective units in the pixel 21-3.

As illustrated in FIG. 16, the pixel 21-3 has a different configurationfrom the pixel 21 of FIG. 4 in that an engraved light shieldingelectrode 57 b-2 is disposed on the light incident surface side of theFD unit 53 side of the PD 52, and an engraved light shielding electrode57 b-1 is disposed on the opposite surface side of the opposite sidethereto. In addition, the pixel 21-3 has common components with thepixel 21 of FIG. 4 in other parts, the common components are denoted bythe same reference numerals and thus the detailed description thereofwill be omitted. In other words, the pixel 21-3 is configured to includea transfer transistor 61, an amplifying transistor 62, a selectiontransistor 63, and a reset transistor 64, and is connected to a verticalsignal line 23.

Further, in the pixel 21-3, light shielding electrode applying voltagesV_(FD) and V_(RD) are respectively supplied from the vertical drivingunit 13 to the engraved light shielding electrodes 57 b-1 and 57 b-2 inorder to apply the potentials described above with reference to FIG. 15to the engraved light shielding electrodes 57 b-1 and 57 b-2.

FIG. 17 illustrates, in order from the top, the selection signal SEL,the reset signal RES, the transfer signal TG, the light shieldingelectrode applying voltages V_(FD)(1) and V_(RD)(2), the light shieldingelectrode applying voltages V_(RD)(1) and V_(RD)(2), the potential levelV_(FD) of the FD unit 53, and the potential level V_(SIG) of thevertical signal line 23.

Here, it is possible to select either the light shielding electrodeapplying voltage V_(RD)(1) or the light shielding electrode applyingvoltage V_(RD)(2) for use in response to the operation of the pixel21-3. For example, the light shielding electrode applying voltageV_(RD)(1) is selected for use in a case of performing a normal expectedoperation. In contrast, the light shielding electrode applying voltageV_(RD)(2) is selected for use in a case of performing a pinningenhancement operation and a transfer assist enhancement operation. Inthe same manner, it is possible to select either the light shieldingelectrode applying voltage V_(RD)(1) or the light shielding electrodeapplying voltage V_(RD)(2) for use in response to the operation of thepixel 21-3. For example, the light shielding electrode applying voltageV_(RD)(1) is selected for use in a case of performing a normal expectedoperation. In contrast, the light shielding electrode applying voltageV_(RD)(2) is selected for use in a case of performing a transfer assistoperation of approaching the vicinity of the FD unit 53 once.

Further, in FIG. 17, a timing t1 is a timing at which selecting thepixel 21-3 as a pixel which outputs a pixel signal is started, and atiming t2 is a timing at which charge transfer from the PD 52 to the FDunit 53 is started. Further, a timing t3 is a timing at which selectingthe pixel 21-3 as a pixel which outputs a pixel signal is terminated.

First, if the accumulation of charges of the PD 52 is started before thetiming t1 at which selecting the pixel 21-3 is started, the lightshielding electrode applying voltage V_(RD)(1) is switched from the lowlevel to the high level, and the light shielding electrode applyingvoltage V_(FD)(2) is switched from the low level to the high level.Further, similarly, the light shielding electrode applying voltagesV_(RD)(1) and V_(RD)(2) are switched from the low level to the highlevel. Thus, a negative potential is applied to the engraved lightshielding electrodes 57 b-1 and 57 b-2. In addition, the low level ofthe transfer signal TG is set to a negative potential and during aperiod other than the charge transfer period, a negative potential isapplied to the gate electrode 54 of the transfer transistor 61 accordingto the transfer signal TG.

Accordingly, during a period of accumulation of charges in the PD 52, anegative potential is applied to the gate electrode 54 and the engravedlight shielding electrodes 57 b-1 and 57 b-2, and as illustrated in FIG.15A, a force pushing electrons e to the center of the PD 52 isgenerated.

Then, at the timing t1, the selection signal SEL is at a high level suchthat the pixel 21-3 is selected; and the reset signal RES is at a highlevel such that the potential level V_(FD) of the FD unit 53 is reset.In other words, the FD unit 53 is in a state in which chargestransferred to the FD unit 53 prior to the present process are left, andthe charges are discharged to the power supply voltage. As a consequenceof this, the potential level V_(SIG) of the vertical signal line 23varies depending on the potential level V_(FD) (that is, a reset level)of the FD unit 53. Thereafter, the reset signal RES is at a low leveland the potential level V_(FD) of the FD unit 53 and the potential levelV_(SIG) of the vertical signal line 23 are stable, and then thepotential level V_(SIG) of the vertical signal line 23 is read as apotential of a reset level to the column processing unit 14 of FIG. 1.

Next, at the timing t2, the transfer signal TG is at a high level suchthat the charges accumulated in the PD 52 are transferred to the FD unit53. In other words, at this time, a positive potential is applied to thegate electrode 54 of the transfer transistor 61 according to thetransfer signal TG. Further, at the timing t2, the light shieldingelectrode applying voltage V_(RD)(1) is at a low level such that 0 V isapplied to the engraved light shielding electrode 57 b-2.

Accordingly, when charges are transferred from the PD 52, a negativepotential is applied to the engraved light shielding electrode 57 b-1,whereas 0 V is applied to the engraved light shielding electrode 57 b-1,and thus a positive potential is applied to the gate electrode 54. Thus,as illustrated in FIG. 15B, the flow of electrons e to the gateelectrode 54 located on the engraved light shielding electrode 57 a-2side is assisted.

Further, at the timing t2, the light shielding electrode applyingvoltage V_(RD)(2) is switched from the first high level to a second highlevel of a higher level. Accordingly, if the light shielding electrodeapplying voltage V_(RD)(2) is selected for use, when charges aretransferred from the PD 52, a negative potential corresponding to thesecond high level which is higher than the negative potentialcorresponding to the first high level is applied to the engraved lightshielding electrode 57 b-1.

In addition, the light shielding electrode applying voltage V_(RD)(2) isat a low level at a predetermined timing before the timing t2, and thus0 V is applied to the engraved light shielding electrode 57 b-2. Thus,prior to the charge transfer, an assist of causing electrons e toapproach the vicinity of the FD unit 53 is performed first.

Then, if charges are transferred from the PD 52 to the FD unit 53, thepotential level V_(FD) of the FD unit 53 and the potential level V_(SIG)of the vertical signal line 23 vary depending on the amount of chargestransferred to the FD unit 53. Thereafter, after the transfer signal TGis at a low level and the transfer of charges is terminated and thepotential level V_(FD) of the FD unit 53 and the potential level V_(SIG)of the vertical signal line 23 are stable, the potential level V_(SIG)of the vertical signal line 23 is read out to the column processing unit14 of FIG. 1 as a potential of the pixel signal level.

Thereafter, at the timing t3, the selection signal SEL is at a low leveland thus the selection of the pixel 21-3 is terminated. At this time,the light shielding electrode applying voltage V_(RD)(1) is switchedfrom a high level to a low level, and the light shielding electrodeapplying voltage V_(RD)(2) is switched from the second high level to thelow level.

Next, FIGS. 18A to 18C are diagrams illustrating a fifth configurationexample of the pixel 21 included in the solid-state imaging device 11.

FIG. 18A illustrates a cross-sectional configuration example of thepixel 21-4 which is the fifth configuration example, FIG. 18Billustrates a planar configuration example of the pixel 21-4 as viewedfrom the opposite surface side, and FIG. 18C illustrates a planarconfiguration example of the pixel 21-4 as viewed from the lightincident surface side.

As illustrated in FIGS. 18A to 18C, the pixel 21-4 has a differentconfiguration from the pixel 21 of FIGS. 2A to 2C in that the engravedlight shielding electrode 57 is divided into the engraved lightshielding electrodes 57 b-1 and 57 b-2. In addition, otherwise, thepixel 21-4 has a different configuration from the pixel 21 of FIGS. 2Ato 2C in that a planar electrode 72 is laminated on the opposite surfaceside of the semiconductor substrate 51 through the insulating film 71,and a transparent conductive film 74 is laminated on the light incidentsurface side of the semiconductor substrate 51 through the barrier metal73. In addition, otherwise, the pixel 21-4 has common components withthe pixel 21 of FIGS. 2A to 2C, the common components are denoted by thesame reference numerals and thus the detailed description thereof willbe omitted. In other words, the pixel 21-4 has a configuration common tothe pixel 21 of FIGS. 2A to 2C in that a PD 52 and an FD unit 53 areformed on the semiconductor substrate 51 and a gate electrode 54 islaminated on an opposite surface side of the semiconductor substrate 51.

Here, in the pixel 21-4, the engraved light shielding electrodes 57 b-1and 57 b-2 are configured in the same manner as the engraved lightshielding electrodes 57 b-1 and 57 b-2 of the pixel 21-3 illustrated inFIGS. 14A to 14C. Further, the insulating film 71, the planar electrode72, the barrier metal 73, and the transparent conductive film 74 in thepixel 21-4 are configured in the same manner as the insulating film 71,the planar electrode 72, the barrier metal 73, and the transparentconductive film 74 of the pixel 21-1 illustrated in FIGS. 6A to 6C.

An operation of a potential applied during the charge accumulationperiod and during the charge transfer period will be described withreference to FIGS. 19A and 19B.

FIG. 19A illustrates the pixel 21-4 during the charge accumulationperiod, and FIG. 19B illustrates the pixel 21-4 during the chargetransfer period. In addition, the light incident on the pixel 21-4 isconverted into electrons e in the PD 52. Further, as illustrated inFIGS. 19A and 19B, the light incident on the pixel 21-4 in an obliquedirection is prevented from leaking to other adjacent pixels 21 by beingreflected on the engraved light shielding electrode 57.

As illustrated in FIG. 19A, in the pixel 21-4, a negative potential isapplied to the gate electrode 54, the engraved light shieldingelectrodes 57 b-1 and 57 b-2, the planar electrode 72, and thetransparent conductive film 74 during the charge accumulation period.Thus, as indicated by the hollow arrows in FIG. 19A, a force pushingelectrons e to the center of the PD 52 is generated. Accordingly, thepixel 21-4 can deepen the potential well of the PD 52 during the chargeaccumulation period and increase the saturation charge amount of the PD52. Further, in the pixel 21-4, it is possible to suppress thegeneration of a dark current by applying a negative potential.

Further, during the charge transfer period, in the pixel 21-4, anegative potential is applied to the engraved light shielding electrodes57 b-1 and 57 b-2 and the transparent conductive film 74, whereas apositive potential is applied to the gate electrode 54 and the planarelectrode 72. Thus, as indicated by the hollow arrows in FIG. 19B, aforce pushing electrons e to the center of the PD 52 and the oppositesurface is generated. Accordingly, as indicated by the hollow arrows ofa dashed line in FIG. 19B, in the pixel 21-4, it is possible to assistthe flow of the electrons e to the gate electrode 54 which is located onthe opposite surface, and to improve the transfer performance of chargesfrom the PD 52 to the FD unit 53.

In this manner, it is possible to increase the saturation charge amountof the PD 52 and to suppress the generation of a dark current during thecharge accumulation period, whereas it is possible to improve thetransfer performance of charges during the charge transfer period,thereby improving the characteristics of the pixel 21-4.

Next, a driving method of the pixel 21-4 will be described withreference to FIGS. 20 and 21.

FIG. 20 illustrates a circuit configuration of the pixel 21-4. FIG. 21illustrates a drive signal supplied to the pixel 21-4 and potentials ofrespective units in the pixel 21-4.

As illustrated in FIG. 20, the pixel 21-4 has a different configurationfrom the pixel 21 of FIG. 4 in that an engraved light shieldingelectrode 57 c-2 is disposed on the light incident surface side of theFD unit 53 side of the PD 52, and an engraved light shielding electrode57 c-1 is disposed on the opposite surface side of the opposite sidethereto. Further, the pixel 21-4 has a different configuration from thepixel 21 of FIG. 4 in that a planar electrode 72 is disposed on theopposite surface side of the sensor layer 32 and a transparentconductive film 74 is disposed on the light incident surface side of thesensor layer 32. In addition, the pixel 21-4 has common components withthe pixel 21 of FIG. 4 in other parts, the common components are denotedby the same reference numerals and thus the detailed description thereofwill be omitted. In other words, the pixel 21-4 is configured to includea transfer transistor 61, an amplifying transistor 62, a selectiontransistor 63, and a reset transistor 64, and is connected to a verticalsignal line 23.

Further, in the pixel 21-4, light shielding electrode applying voltagesV_(FD) and V_(RD) are respectively supplied from the vertical drivingunit 13 to the engraved light shielding electrodes 57 c-1 and 57 c-2 inorder to apply the potentials described above with reference to FIGS.19A and 19B to the engraved light shielding electrodes 57 c-1 and 57c-2. Similarly, in the pixel 21-4, a planar electrode applying voltageV_(TSF) is supplied from the vertical driving unit 13 to the planarelectrode 72 in order to apply the potentials described above withreference to FIGS. 19A and 19B to the planar electrode 72. Further, atransparent conductive film applying voltage V_(TR) is supplied from thevertical driving unit 13 to the transparent conductive film 74 in orderto apply the potentials described above with reference to FIGS. 19A and19B to the transparent conductive film 74.

FIG. 21 illustrates, in order from the top, the selection signal SEL,the reset signal RES, the transfer signal TG, the transparent conductivefilm applying voltages V_(TR)(1) and V_(TR)(2), the light shieldingelectrode applying voltages V_(FD)(1) and V_(FD)(2), the light shieldingelectrode applying voltages V_(RD)(1) and V_(RD)(2), the planarelectrode applying voltages V_(TSF)(1) and V_(TSF)(2), the potentiallevel V_(FD) of the FD unit 53, and the potential level V_(SIG) of thevertical signal line 23.

Here, the light shielding electrode applying voltage V_(FD)(1) and thetransparent conductive film applying voltage V_(TR)(1) are common, andthe light shielding electrode applying voltage V_(FD)(2) and thetransparent conductive film applying voltage V_(RD)(2) are common.Further, the transparent conductive film applying voltages V_(TR)(1) andV_(TR)(2), the light shielding electrode applying voltage V_(FD)(1) andV_(FD)(2), and the light shielding electrode applying voltages V_(RD)(1)and V_(RD)(2) are represented as inverted signals, and when the applyingvoltages are at high levels, a negative potential is applied. Inaddition, the low level of the planar electrode applying voltagesV_(TSF)(1) and V_(TSF)(2) is a negative potential, and the high level ofthe planar electrode applying voltage V_(TSF)(1) and V_(TSF)(2) is apositive potential.

Further, it is possible to select either a pair of the light shieldingelectrode applying voltage V_(FD)(1) and the transparent conductive filmapplying voltage V_(TR)(1) or a pair of the light shielding electrodeapplying voltage V_(FD)(2) and the transparent conductive film applyingvoltage V_(TR)(2) for use in response to the operation of the pixel21-4. For example, the pair of the light shielding electrode applyingvoltage V_(FD)(1) and the transparent conductive film applying voltageV_(TR)(1) is selected for use in a case of performing a normal expectedoperation. In contrast, the pair of the light shielding electrodeapplying voltage V_(FD)(2) and the transparent conductive film applyingvoltage V_(TR)(2) is selected for use in a case of performing a pinningenhancement operation and a transfer assist enhancement operation.

In the same manner, it is possible to select either the light shieldingelectrode applying voltage V_(RD)(1) or the light shielding electrodeapplying voltage V_(RD)(2) for use in response to the operation of thepixel 21-4. For example, the light shielding electrode applying voltageV_(RD)(1) is selected for use in a case of performing a normal expectedoperation. In contrast, the light shielding electrode applying voltageV_(RD)(2) is selected for use in a case of performing a transfer assistoperation of approaching the vicinity of the FD unit 53 once.

In the same manner, it is possible to select either the planar electrodeapplying voltage V_(TSF)(1) or the planar electrode applying voltageV_(TSF)(2) for use in response to the operation of the pixel 21-4. Forexample, the planar electrode applying voltage V_(TSF)(1) is selectedfor use in a case of performing a normal expected operation. Incontrast, the planar electrode applying voltage V_(TSF)(2) is selectedfor use in a case of performing an operation of performing a transferwhile causing charges to approach the vicinity of the opposite surface.

Further, in FIG. 21, a timing t1 is a timing at which selecting thepixel 21-4 as a pixel which outputs a pixel signal is started, and atiming t2 is a timing at which charge transfer from the PD 52 to the FDunit 53 is started. Further, a timing t3 is a timing at which selectingthe pixel 21-4 as a pixel which outputs a pixel signal is terminated.

First, if the accumulation of charges of the PD 52 is started before thetiming t1 at which selecting the pixel 21-4 is started, the lightshielding electrode applying voltage V_(FD)(1) and the transparentconductive film applying voltage V_(TR)(1) are switched from the lowlevel to the high level. Further, similarly, the light shieldingelectrode applying voltage V_(FD)(2) and the transparent conductive filmapplying voltage V_(TR)(2) are switched from the low level to a firsthigh level. Furthermore, similarly, the light shielding electrodeapplying voltages V_(RD)(1) and V_(RD)(2) are switched from the lowlevel to the high level. Thus, a negative potential is applied to theengraved light shielding electrodes 57 c-1 and 57 c-2 and thetransparent conductive film 74. Further, at this time, the planarelectrode applying voltages V_(TSF)(1) and V_(TSF)(2) are at a lowlevel, and a negative potential is applied to the planar electrode 72.In addition, the low level of the transfer signal TG is set to anegative potential and during a period other than the charge transferperiod, a negative potential is applied to the gate electrode 54 of thetransfer transistor 61 according to the transfer signal TG.

Accordingly, during a period of accumulation of charges in the PD 52, anegative potential is applied to the gate electrode 54, the engravedlight shielding electrodes 57 b-1 and 57 b-2, the planar electrode 72,and the transparent conductive film 74, and as illustrated in FIG. 19A,a force pushing electrons e to the center of the PD 52 is generated.

Then, at the timing t1, the selection signal SEL is at a high level suchthat the pixel 21-4 is selected; and the reset signal RES is at a highlevel such that the potential level V_(FD) of the FD unit 53 is reset.In other words, the FD unit 53 is in a state in which chargestransferred to the FD unit 53 prior to the present process are left, andthe charges are discharged to the power supply voltage. As a consequenceof this, the potential level V_(SIG) of the vertical signal line 23varies depending on the potential level V_(FD)(that is, a reset level)of the FD unit 53. Thereafter, the reset signal RES is at a low leveland the potential level V_(FD) of the FD unit 53 and the potential levelV_(SIG) of the vertical signal line 23 are stable, and then thepotential level V_(SIG) of the vertical signal line 23 is read as apotential of a reset level to the column processing unit 14 of FIG. 1.

Next, at the timing t2, the transfer signal TG is at a high level suchthat the charges accumulated in the PD 52 are transferred to the FD unit53. In other words, at this time, a positive potential is applied to thegate electrode 54 of the transfer transistor 61 according to thetransfer signal TG. Further, simultaneously with the transfer signal TG,the planar electrode applying voltage V_(TSF)(1) is at a low level suchthat a positive potential is applied to the planar electrode 72according to the planar electrode applying voltage V_(TSF)(1).

Accordingly, when charges are transferred from the PD 52, a negativepotential is applied to the engraved light shielding electrode 57 andthe transparent conductive film 74, whereas a positive potential isapplied to the gate electrode 54 and the planar electrode 72, such thatas illustrated in FIG. 19B, the flow of electrons e to the gateelectrode 54 is assisted.

Further, at the timing t2, the light shielding electrode applyingvoltage V_(FD)(2) and the transparent conductive film applying voltageV_(TR)(2) are switched from the first high level to a second high levelof a higher level. Accordingly, if the light shielding electrodeapplying voltage V_(FD)(2) and the transparent conductive film applyingvoltage V_(RD)(2) are selected for use, when charges are transferredfrom the PD 52, a negative potential corresponding to the second highlevel which is higher than the negative potential corresponding to thefirst high level is applied to the engraved light shielding electrode 57and the transparent conductive film 74.

In addition, the light shielding electrode applying voltage V_(RD)(2) isat a low level at a predetermined timing before the timing t2, and thus0 V is applied to the engraved light shielding electrode 57 b-2. Thus,prior to the charge transfer, an assist of causing electrons e toapproach the vicinity of the FD unit 53 is performed first.

Then, if charges are transferred from the PD 52 to the FD unit 53, thepotential level V_(FD) of the FD unit 53 and the potential level V_(SIG)of the vertical signal line 23 vary depending on the amount of chargestransferred to the FD unit 53. Thereafter, after the transfer signal TGand the planar electrode applying voltage V_(TSF)(1) are at a low leveland the transfer of charges is terminated and the potential level V_(FD)of the FD unit 53 and the potential level V_(SIG) of the vertical signalline 23 are stable, the potential level V_(SIG) of the vertical signalline 23 is read out to the column processing unit 14 of FIG. 1 as apotential of the pixel signal level.

Here, the planar electrode applying voltage V_(TSF)(2) is at a highlevel at a predetermined timing later than the planar electrode applyingvoltage V_(TSF)(1). In other words, when the planar electrode applyingvoltage V_(TSF)(2) is selected for use, a positive potential is appliedto the planar electrode 72 at a timing later than a timing at which apositive potential is applied to the gate electrode 54. Thus, forexample, when charges are transferred from the PD 52 to the FD unit 53,electrons e are drawn to the opposite surface side of the semiconductorsubstrate 51 after the flow of electrons e to the gate electrode 54 isformed, such that the leakage of electrons e along the opposite surfaceof the semiconductor substrate 51 is prevented.

Thereafter, at the timing t3, the selection signal SEL is at a low leveland thus the selection of the pixel 21-4 is terminated. At this time,the light shielding electrode applying voltage V_(FD)(2) and thetransparent conductive film applying voltage V_(TR)(2) are switched froma high level to a low level. In the same manner, the light shieldingelectrode applying voltage V_(FD)(2) and the transparent conductive filmapplying voltage V_(TR)(2) are switched from the second high level tothe low level.

Further, the solid-state imaging device 11 described above can beapplied to various electronic apparatuses including imaging systems suchas digital still cameras and digital video cameras, mobile phones withan imaging function, or other apparatuses with an imaging function.

FIG. 22 is a block diagram illustrating a configuration example of animaging apparatus mounted on an electronic apparatus.

As illustrated in FIG. 22, an imaging apparatus 101 is configured toinclude an optical system 102, an imaging device 103, a signalprocessing circuit 104, a monitor 105, and a memory 106, and is capableof capturing still images and moving images.

The optical system 102 is configured to include one or a plurality oflenses, and guides image light (incident light) from an object to theimaging device 103 so as to focus the image light on a light receivingsurface (sensor unit) of the imaging device 103.

As the imaging device 103, a solid-state imaging device 11 includingphase difference pixels 21 a of various configuration examples describedabove is applied. Electrons are accumulated in the imaging device 103for a fixed period, according to an image focused on the light receivingsurface through the optical system 102. Thus, signals according to theelectrons accumulated in the imaging device 103 are supplied to thesignal processing circuit 104.

The signal processing circuit 104 performs various signal processes onthe pixel signals which are output from the imaging device 103. Theimage (image data) obtained by the signal processing circuit 104performing the signal processes is supplied to and displayed on themonitor 105, or is supplied to and stored (recorded) in the memory 106.

In the imaging apparatus 101 configured in this manner, it is possibleto obtain, for example, an image with less noise even at a low intensityof illumination by employing the solid-state imaging device 11 includingthe pixel 21 of various configuration examples described above.

In addition, the present technology may have the followingconfigurations.

(1)

A solid-state imaging device including:

a photoelectric conversion unit that generates charges byphotoelectrically converting light;

a light shielding unit that is formed by engraving a semiconductorsubstrate on which the photoelectric conversion unit is formed, so as tosurround an outer periphery of the photoelectric conversion unit; and

a transfer transistor that transfers charges generated in thephotoelectric conversion unit,

wherein during a charge accumulation period in which charges areaccumulated in the photoelectric conversion unit, a potential thatrepels the charges is supplied to the light shielding unit and a gateelectrode of the transfer transistor, and

wherein during a charge transfer period in which charges are transferredfrom the photoelectric conversion unit, a potential that repels thecharges is supplied to the light shielding unit and a potential thatattracts the charges is supplied to the gate electrode of the transfertransistor.

(2)

The solid-state imaging device according to (1), further including:

a conductive film having optical transparency laminated on a lightincident surface side on which light enters the photoelectric conversionunit, with respect to the semiconductor substrate on which thephotoelectric conversion unit is formed,

wherein during the charge accumulation period and during the chargetransfer period, the potential that repels the charges is supplied tothe conductive film.

(3)

The solid-state imaging device according to (1) or (2), furtherincluding:

a planar electrode laminated in a plane manner on an opposite surfaceside which is opposite to the light incident surface side on which lightenters the photoelectric conversion unit, with respect to thesemiconductor substrate on which the photoelectric conversion unit isformed,

wherein during the charge accumulation period, the potential that repelsthe charges is supplied to the planar electrode, and

wherein during the charge transfer period, the potential that attractsthe charges is supplied to the planar electrode.

(4)

The solid-state imaging device according to any one of (1) to (3),

wherein a part of the light shielding unit is formed on a light incidentsurface side on which light enters the photoelectric conversion unit,with respect to the semiconductor substrate on which the photoelectricconversion unit is formed, and another part of the light shielding unitis formed on an opposite surface side which is opposite to the lightincident surface side, and respective potentials are independentlysupplied to the part and the other part of the light shielding unit.

(5)

The solid-state imaging device according to any one of (1) to (4),further including:

a conductive film having optical transparency laminated on a lightincident surface side on which light enters the photoelectric conversionunit, with respect to the semiconductor substrate on which thephotoelectric conversion unit is formed, and

a planar electrode laminated in a plane manner on an opposite surfaceside which is opposite to the light incident surface side on which lightenters the photoelectric conversion unit, with respect to thesemiconductor substrate on which the photoelectric conversion unit isformed,

wherein a part of the light shielding unit is formed on the lightincident surface side on which light enters the photoelectric conversionunit, with respect to the semiconductor substrate on which thephotoelectric conversion unit is formed, and the other part of the lightshielding unit is formed on an opposite surface side which is oppositeto the light incident surface side, and respective potentials areindependently supplied to the gate electrode of the transfer transistor,the conductive film, the planar electrode, the part and the other partof the light shielding unit.

(6)

A driving method of a solid-state imaging device including aphotoelectric conversion unit that generates charges byphotoelectrically converting light, a light shielding unit that isformed by engraving a semiconductor substrate on which the photoelectricconversion unit is formed, so as to surround an outer periphery of thephotoelectric conversion unit, and a transfer transistor that transferscharges generated in the photoelectric conversion unit, including:

supplying a potential that repels the charges to the light shieldingunit and a gate electrode of the transfer transistor, during a chargeaccumulation period in which charges are accumulated in thephotoelectric conversion unit; and

supplying the potential that repels the charges to the light shieldingunit and supplying a potential that attracts the charges to the gateelectrode of the transfer transistor, during a charge transfer period inwhich charges are transferred from the photoelectric conversion unit.

(7)

An electronic apparatus including:

a solid-state imaging device including:

a photoelectric conversion unit that generates charges byphotoelectrically converting light;

a light shielding unit that is formed by engraving a semiconductorsubstrate on which the photoelectric conversion unit is formed, so as tosurround an outer periphery of the photoelectric conversion unit; and

a transfer transistor that transfers charges generated in thephotoelectric conversion unit,

wherein during a charge accumulation period in which charges areaccumulated in the photoelectric conversion unit, a potential thatrepels the charges is supplied to the light shielding unit and a gateelectrode of the transfer transistor, and

wherein during a charge transfer period in which charges are transferredfrom the photoelectric conversion unit, a potential that repels thecharges is supplied to the light shielding unit and a potential thatattracts the charges is supplied to the gate electrode of the transfertransistor.

It should be understood that the disclosure is not limited to theabove-described embodiments, but may be modified into various forms in arange without departing from a gist of the disclosure.

What is claimed is:
 1. An imaging device, comprising: a semiconductorsubstrate having a first side and a second side, wherein the first sideis opposite to the second side; a first trench starting and extendingfrom the first side of the semiconductor substrate towards the secondside of the semiconductor substrate, unobstructed by any other trench,in a cross-sectional view; a second trench starting and extending fromthe second side of the semiconductor substrate towards the first side ofthe semiconductor substrate, unobstructed by any other trench, in thecross-sectional view, wherein each of the first trench and the secondtrench has a depth less than a thickness of the semiconductor substratein the cross-sectional view.
 2. The imaging device according to claim 1,wherein the first trench includes a fixed charge film.
 3. The imagingdevice according to claim 1, wherein the first trench includes aninsulating film.
 4. The imaging device according to claim 1, wherein thefirst trench includes a metal.
 5. The imaging device according to claim1, wherein the first trench includes a light shielding electrode.
 6. Theimaging device according to claim 1, wherein the second trench includesa second fixed charge film.
 7. The imaging device according to claim 1,wherein the second trench includes a second insulating film.
 8. Theimaging device according to claim 1, wherein the second trench includesa metal.
 9. The imaging device according to claim 1, further comprising:a photoelectric conversion region in the semiconductor substrate,wherein the first trench partially surrounds a portion of thephotoelectric conversion region at the first side of the semiconductorsubstrate.
 10. The imaging device according to claim 9, wherein thefirst side is a light-incident side.
 11. The imaging device according toclaim 10, wherein during a charge accumulation period in which chargesare accumulated in the photoelectric conversion region, a firstpotential that repels the charges is supplied to the first trench. 12.The imaging device according to claim 11, wherein during a chargetransfer period in which charges are transferred from the photoelectricconversion unit, another potential that repels the charges is suppliedto the first trench.
 13. The imaging device according to claim 12,further comprising: a conductive film at the light-incident side of thesemiconductor substrate, wherein during the charge accumulation periodand during the charge transfer period, the potential that repels thecharges is supplied to the conductive film.
 14. The imaging deviceaccording to claim 1, further comprising: a planar electrode disposed atthe second side of the semiconductor substrate.
 15. The imaging deviceaccording to claim 1, further comprising a wiring layer disposed at thesecond side of the semiconductor substrate.
 16. An imaging device,comprising: a semiconductor substrate having a first side and a secondside, wherein the first side is opposite to the second side; a firsttrench starting and extending from the first side of the semiconductorsubstrate towards the second side of the semiconductor substrate in across-sectional view; a second trench starting and extending from thesecond side of the semiconductor substrate towards the first side of thesemiconductor substrate, unobstructed by any other trench, in thecross-sectional view; and a photoelectric conversion region in thesemiconductor substrate, wherein the first trench partially surrounds aportion of the photoelectric conversion region at the first side of thesemiconductor substrate, wherein the first side is a light-incidentside, and wherein a depth of the second trench is less than thethickness of the semiconductor substrate, unobstructed by any othertrench, in the cross-sectional view.
 17. The imaging device according toclaim 16, wherein during a charge accumulation period in which chargesare accumulated in the photoelectric conversion region, a firstpotential that repels the charges is supplied to the first trench. 18.An imaging device, comprising: a semiconductor substrate having a firstside and a second side, wherein the first side is opposite to the secondside; a first trench starting and extending from the first side of thesemiconductor substrate towards the second side of the semiconductorsubstrate, unobstructed by any other trench, in a cross-sectional view;a second trench starting and extending from the second side of thesemiconductor substrate towards the first side of the semiconductorsubstrate, unobstructed by any other trench, in the cross-sectionalview, wherein the first trench extends to a point that is a firstdistance from the first side of the semiconductor substrate, wherein thesecond trench extends to a point that is a second distance from thefirst side of the semiconductor substrate, and wherein the seconddistance is less than the first distance, and wherein an electrode isdisposed in the second trench.